Fast cell selection in a mobile wireless device

ABSTRACT

A method and apparatus for fast cell selection by a mobile wireless device. The mobile wireless device detects when a first wireless cell fails a set of stored suitability criteria and searches for and locates a set of candidate wireless cells to associate with. The mobile wireless device measures at least one received signal metric for each candidate wireless cell in the set of candidate wireless cells. When a candidate cell in the set of candidate wireless cells is identically the first wireless cell, the mobile wireless device evaluates the suitability of the candidate wireless cell using the stored set of suitability criteria for the first wireless cell and the measured at least one received signal metric for the candidate wireless cell. The mobile wireless communication device associates with the candidate wireless cell when the candidate wireless cell meets the stored set of suitability criteria.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application takes priority under 35 U.S.C. 119(e) to U.S.Provisional Patent Application Ser. No. 61/358,335 entitled, “METHOD ANDAPPARATUS FOR FAST CELL SELECTION IN A MOBILE WIRELESS DEVICE” byVasudevan et al. filed Jun. 24, 2010 which is incorporated by referenceherein in its entirety for all purposes.

TECHNICAL FIELD

The described embodiments relate generally to wireless mobilecommunications. More particularly, a method is described for fast cellselection in a mobile wireless communication device.

BACKGROUND OF THE INVENTION

Mobile wireless communication devices, such as a cellular telephone or awireless personal digital assistant, can provide a wide variety ofcommunication services including, for example, voice communication, textmessaging, internet browsing, and electronic mail. Mobile wirelesscommunication devices can operate in a wireless communication network ofoverlapping “cells”, each cell providing a geographic area of wirelesssignal coverage that extends from a radio network subsystem locatedwithin the cell. The radio network subsystem provides an “air interface”through which the mobile wireless communication device can access thewireless communication network. Whether idle or actively connected, amobile wireless communication device can be associated with a “serving”cell in a wireless communication network and be aware of “neighbor”cells to which the mobile wireless communication device can alsoassociate. The quality of the air interface between the mobile wirelesscommunication device and the radio network subsystem can vary based onthe distance between them and on interference included in receivedsignals at either end of the air interface. As the mobile wirelesscommunication device moves further away from the radio networksubsystem, eventually a neighbor cell can provide an equal or betterperforming communication link than the current serving cell. The mobilewireless communication device can include a process for determining ifand when to switch cells with which it associates. If the mobilewireless communication device is actively connected to the serving cell,then the process of switching to a neighbor cell is known as “handoff.”For a mobile wireless communication device that is associated with aserving cell in an “idle” state, the process of associating with aneighbor cell is known as “cell reselection.”

When a mobile wireless communication device seeks to associate with awireless communication network, such as after a power on initialization,the mobile wireless communication device can search for cells located inits vicinity. Initially locating and connecting to a serving cell by amobile wireless communication device can be referred to as “cellselection”. If a cell is located that is deemed suitable to provide awireless communication link, e.g. when signals received by the mobilewireless communication device from the radio network subsystem locatedin the cell exceeds certain performance quality metrics, then the mobilewireless communication device can associate with that cell. The mobilewireless communication device can be referred to as being “camped” on aparticular “serving” cell in the wireless communication network ofcells. While camped on the serving cell, the mobile wirelesscommunication device can listen to messages broadcast from the servingcell's radio network subsystem as well as from other radio networksubsystems located in neighbor cells. System information that specifiescertain properties of the serving cell and its neighbor cells can bebroadcast regularly by the serving cell's radio network subsystem. Ifthe mobile wireless communication device determines that a neighbor cellcan provide a higher quality communication link than a current servingcell, then the mobile wireless communication device can disassociatefrom the current serving cell and associate with the neighbor cell, in aprocess known as “cell reselection”.

Initial cell selection and cell reselection can include reading a numberof different system information messages transmitted by the radionetwork subsystems in the wireless communication network. Each systeminformation message can be transmitted at regular intervals. By waitingto read the system information messages when broadcast, the mobilewireless communication device can be assured of using the latest systemparameter values during the cell evaluation process. Some of the systeminformation messages can change infrequently, however, and the mobilewireless communication device can incur an unnecessary delay whenwaiting to read the most recent system information if the sameinformation has been read before. For example, when there is a momentaryor short time interval loss of service by the mobile wirelesscommunication device or when the mobile wireless communication devicereacquires the same cell as previously used, it can be desired toshorten the lengthy cell search and selection procedure by reusingsystem parameters that were read earlier and stored in the mobilewireless communication device.

SUMMARY OF DESCRIBED EMBODIMENTS

This paper describes various embodiments that relate to methods andapparatus for fast cell selection by a mobile wireless communicationdevice in a wireless communication network.

In a representative embodiment, a method includes at least the followingsteps performed by a mobile wireless communication device. The mobilewireless communication device detects that a first wireless cell withwhich it is associated fails at least one criterion in a set ofsuitability criteria. The set of suitability criteria are stored in themobile wireless communication device. After the first wireless cellfails suitability, the mobile wireless communication device searches forand locates a set of candidate wireless cells with which to associate.The mobile wireless communication device measures at least one receivedsignal metric for each candidate wireless cell in the set of candidatewireless cells. When the mobile wireless communication device determinesthat a candidate cell in the set of candidate wireless cells isidentically the first wireless cell, the mobile wireless communicationdevice evaluates the suitability of the candidate wireless cell. Thesuitability evaluation uses one or more criteria in the stored set ofsuitability criteria for the first wireless cell and the measured atleast one received signal metric for the candidate wireless cell. Themobile wireless communication device associates with the candidatewireless cell when the candidate wireless cell satisfies one or morecriteria in the stored set of suitability criteria.

In another representative embodiment, a mobile wireless communicationdevice includes an application processor and a transceiver configured toselect a cell in a wireless communication network with which to connect.The mobile wireless communication device is configured to select thecell by detecting a loss of radio frequency connection between thetransceiver in the mobile wireless communication device and a first cellin the wireless communication network. The mobile wireless communicationdevice is configured to locate a set of candidate cells in the wirelesscommunication network with which to connect. The mobile wirelesscommunication device is configured to determine a subset of locatedcandidate cells that match to cell suitability criteria stored in themobile wireless communication device. The mobile wireless communicationdevice is configured to select a cell in the subset of located candidatecells based on measuring cell suitability using the stored cellsuitability criteria and associate with the selected cell. The cellsuitability criteria are stored in the mobile wireless communicationdevice prior to detecting the loss of radio frequency connection.

In a further representative embodiment, a computer readable medium forstoring non-transitory computer program code executable by a processorin a mobile wireless communication device for selecting a cell in awireless network with which the mobile wireless communication deviceassociates includes at least the following non-transitory computerprogram codes. A non-transitory computer program code for detecting thata first cell fails one or more suitability criteria stored in the mobilewireless communication device. A non-transitory computer program codefor searching for and locating a set of candidate cells with which toassociate the mobile wireless communication device. A non-transitorycomputer program code for determining if one of the candidate cells inthe set of candidate cells is identically the first cell. Anon-transitory computer program code for evaluating suitability of thefirst cell using the one or more stored suitability criteria when one ofthe candidate cells is the first cell. A non-transitory computer programcode for associating with the first cell when one of the candidate cellsin the set of candidate cells is identically the first cell and thefirst cell is suitable.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and the advantages thereof may best be understood byreference to the following description taken in conjunction with theaccompanying drawings.

FIG. 1 illustrates a mobile wireless communication device located withina wireless cellular communication network.

FIG. 2 illustrates a discontinuous reception cycle for a mobile wirelesscommunication device.

FIG. 3 illustrates a sequence of transmitted system information blocksused for cell selection and reselection.

FIG. 4 illustrates a prior art method for performing cell selection.

FIG. 5 illustrates a representative method for performing cell selectionwith early suitability criteria evaluation.

FIG. 6 illustrates a representative method for evaluating cellsuitability and associating with a suitable cell.

FIG. 7 illustrates a representative method for testing cell suitabilityand associated with a suitable cell.

FIG. 8 illustrates processing units of a mobile wireless communicationdevice.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, numerous specific details are set forth toprovide a thorough understanding of the concepts underlying thedescribed embodiments. It will be apparent, however, to one skilled inthe art that the described embodiments may be practiced without some orall of these specific details. In other instances, well known processsteps have not been described in detail in order to avoid unnecessarilyobscuring the underlying concepts.

A mobile wireless communication device 106 can include the capability toconnect seamlessly with a wireless communication network 100 ofoverlapping wireless communication cells, each wireless communicationcell covering a geographic area extending from a radio network subsystem104 as illustrated in FIG. 1. The mobile wireless communication device106 can receive communication signals from radio network subsystemslocated in different cells in the wireless communication network 100,and each cell can be located at a different distance from the mobilewireless communication device 106. As signal strength of a wirelesscommunication signal decays proportionally to the square of the distancebetween a transmitting end and a receiving end, the mobile wirelesscommunication device 106 can monitor the received signal strength fromseveral different cells in the wireless communication network 100 todetermine a cell having the strongest received signal at any given time.As the mobile wireless communication device 106 changes locations withina wireless communication network 100, the received signal strength canvary substantially, and thus the cell from which the mobile wirelesscommunication device 106 receives the strongest signal can change.

After a “power on” initialization, or similarly when entering a “new”wireless communication network, the mobile wireless communication device106 can seek to associate with a cell in the wireless communicationnetwork 100, i.e. to “select” a cell. A radio network subsystem in eachcell of the wireless communication network 100 can broadcast a series ofsystem information messages at regular intervals that identify salientcharacteristics of the radio network subsystem as well as certainproperties of radio network subsystems located in neighbor cells. Basedon measurements of received signal strength, or other quality metricssuch as carrier to interference ratios, the mobile wirelesscommunication device 106 can associate with a radio network subsystem104, thereby “selecting” a particular cell within the wirelesscommunication network 100 as a “serving” cell 102. The process ofassociating with a “serving” cell can be also known as “camping” on thatcell.

After associating with the serving cell 102, the mobile wirelesscommunication device 106 can initiate connections (such as voice or datacalls) with the wireless communication network 100 through the radionetwork subsystem 104 of the serving cell 102. The radio networksubsystem 104 in the serving cell 102 can also initiate connections tothe mobile wireless communication device 106, as the wireless network100 can be aware of the association between the serving cell 102 and themobile wireless communication device 106. While “camped” on the servingcell 102, the mobile wireless communication device 106 can monitorbroadcast signals from the radio network subsystem 104 that includesystem information to determine if and when to associate with adifferent radio network subsystem 108 in a neighbor cell 110.

System information can be communicated from the radio network subsystem104 in the serving cell 102 to the mobile wireless communication device106 camped on the serving cell through system information messages (alsocalled system information blocks). Parameters associated with a commonfunction can be grouped together in a system information message of aparticular type. As a representative example, the third-generation (3G)mobile communication technology known as Universal MobileTelecommunications System (UMTS), which is developed and maintained bythe 3^(rd) Generation Partnership Project (3GPP), includes a radioresource control (RRC) protocol that organizes system information intoone of a number of different system information blocks (SIBs). In orderto enable mobile wireless communication devices 106 in the serving cell102 to determine which SIBs are broadcast by the radio network subsystem104 and in which specific system frames the SIBs will occur, a masterinformation block (MIB) can be broadcast regularly that can providescheduling information about the SIBs. The MIB can be transmitted on abroadcast control (BCCH) logical channel, which can be mapped to abroadcast (BCH) transport channel.

In a representative embodiment, the MIB can be broadcast once every 8system frames of 10 ms each (i.e. once per 80 ms). The scheduling of theMIB can be thus static and regular, while the scheduling of SIB blocksof different types can be dynamic and irregular. The MIB can bebroadcast frequently by the radio network subsystem 104 in the servingcell 102 to ensure there is low latency when the mobile wirelesscommunication device 106 reads a current MIB; however, the systeminformation for a cell can change at a slower rate than the MIBbroadcast rate, so reading every MIB that is broadcast every 80 ms canbe inefficient. Instead, the mobile wireless communication device 106can receive an indication when system information changes through apaging indication on a paging (PCH) transport channel broadcast by theradio network subsystem 104. As shown in FIG. 2, a mobile wirelesscommunication device 106 can cycle between “sleep” periods and “wake”periods in a cycle known as discontinuous reception (DRX) 202. During a“wake” period 204, the mobile wireless communication device 106 canmonitor a paging indicator channel (PICH) during a paging occasion 208.If system information has changed, as indicated by a message received onthe PICH, then the mobile wireless communication device 106 can read thenext broadcast MIB for additional system information. In between wakeperiods 204, the mobile wireless communication device 106 can conservebattery power by entering sleep periods, during which time one or moreblocks of circuitry, such as radio frequency transceivers, in the mobilewireless communication device 106 can be powered down. The frequency ofpaging occasions can be set by the radio network subsystem 104 in theserving cell 102, while the DRX cycle 202 can be managed by the mobilewireless communication device 106 to ensure the wake periods 204 alignwith the paging occasions 208.

During a paging occasion 208, the mobile wireless communication devicecan evaluate the current serving cell using a set of suitabilitycriteria communicated in one or more system information blocks. FIG. 3illustrates a portion of a sequence 300 of system frames in which amaster information block MIB 302 and two types of system informationblocks 302/306 are transmitted by the radio network subsystem 104 of theserving cell 102 on a broadcast common control channel (BCCH). In theUMTS wireless communication protocol cell reselection parameters for thecurrent serving cell can be transmitted using a system information block302 of type 3 (SIB3), while reselection parameters for a set of neighborcells can be transmitted using a system information block 306 of type 11(SIB11). The system information blocks can repeat at regular intervals,and the repetition frequency for each type of system information blockcan vary. As shown in FIG. 3, the MIB 302 repeats every 8 system frames(80 ms), while SIB3 304 and SIB 11 306 repeat every 128 system frames(1280 ms). (Other SIB types are not shown in FIG. 3 but can be includedin one or more of the system frames marked by an ‘x’.) The maximumrepetition count for all types of system information blocks can belimited to 128 system frames, and thus all system information blocks canbe read over a period of 1.28 seconds. To minimize battery power drain,the mobile wireless communication device 106 can learn the schedule ofSIB transmissions from the MIB 302 and wake to read only those SIBs thatcan be required and can sleep during the time intervals in between.

During a cell selection process, the mobile wireless communicationdevice 106 can wait for a current SIB3 304 in order to evaluatesuitability criteria for the current serving cell 102. As values ofpreviously read SIB3 304 (or other system information blocks) can bestored in memory on the mobile wireless communication device 106, thecell selection process can be accelerated by using previously readvalues for the SIB3 304. Suitability criteria that can be specified inthe SIB3 304 can include a minimum received power level and a minimumreceived signal quality level. During a wake period 204, the mobilewireless communication device 106 can measure a common pilot channel(CPICH) to determine a received signal code power (RSCP) as well as asignal to interference ratio (Ec/Io) and compare the received valuesagainst the parameters read from the SIB3 304. As a representativeembodiment, the mobile wireless communication device 106 in a UMTSwireless communication network 100 can deem a serving cell 102 suitableif the following equations are satisfied.Srxlev>0Squal>0where the parameters Srxlev and Squal can be calculated as follows.Srxlev=Qrxlevmeas−Qrxlevmin−PcompSqual=Qqualmeas−QqualminThe parameters Qrxlevmin, Qqualmin and Pcomp can be specified by theradio network subsystem 104 in the SIB3 304, while the parametersQqualmeas and Qrxlevmeas can be measured by the mobile wirelesscommunication device 106. If the serving cell 102 is found “unsuitable”over a series of consecutive DRX cycles 202, then the mobile wirelesscommunication device can initiate a cell reselection process. The numberof consecutive DRX cycles that can trigger a cell reselection can betransmitted by the radio network subsystem 104 in the SIB3 304. The SIB3304 can also include additional parameters Sintrasearch, Sintersearch,SinterRAT that can trigger an intra-frequency, inter-frequency orinter-“radio access technology” cell search procedure respectively ifthe calculated value Squal falls below a level specified by theseadditional parameters.

FIG. 4 illustrates a portion of a prior art method 400 for a cellselection process for a mobile wireless communication device 106.Initially in step 402, the mobile wireless communication device 106 canbe “in service” associated with the serving cell 102 of the wirelesscommunication network 100. During one or more DRX cycles 202, in step404, the mobile wireless communication device can measure the servingcell 102 signal quality and can determine that the serving cell 102 doesnot satisfy the suitability criteria specified by the SIB3 304parameters. Cell suitability failure can occur because the received andmeasured signal quality falls below certain thresholds in one or moreDRX cycles 202. In step 406, the mobile wireless communication device106 can conduct a search for available cells. The cell search procedurein step 406 can include sub-steps (not shown) that acquire time slot andframe synchronization using synchronization codes followed by adetermination of a primary scrambling code for each cell found. At theend of the cell search in step 406, the mobile wireless communicationdevice 106 can have for each cell found, a Universal Terrestrial RadioAccess (UTRA) Absolute Radio Frequency Channel Number (UARFCN), aprimary scrambling code (PSC), a received signal code power (RSCP) valueand a chip energy (Ec/Io) value.

For the multiple cells found in step 406, the mobile wirelesscommunication device can “rank” the cells according to ranking criteriausing the RSCP and Ec/Io values. For the “best” cell found, the mobilewireless communication device can determine suitability of the cell in aread/evaluation cycle 418 of several steps. In step 408, the mobilewireless communication device 106 can read the MIB on the BCCH. Usingscheduling information from the MIB, the mobile wireless communicationdevice can read in step 410 one or more SIBs, such as SIB3. In step 412,the measured RSCP and Ec/Io values can be compared against suitabilitycriteria read from SIB3 to determine whether the cell is suitable. Ifthe cell satisfies the suitability criteria as determined in step 414,then the cell selection procedure can continue in step 416. If the celldoes not satisfy the suitability criteria, however, then theread/evaluate cycle 418 can repeat using the “next best” cell found inthe cell search of step 406. The read/evaluate cycle 418 can takeseveral seconds to complete before cell selection continues. This timecan lengthen the cell selection procedure even when the mobile wirelesscommunication device 106 finds a previous cell for which suitabilitycriteria can have been already read and stored in the mobile wirelesscommunication device 106.

A faster cell selection process can be accomplished using a method 500shown in FIG. 5. As in FIG. 5, the mobile wireless communication device106 can search for multiple cells in step 406 following a cellsuitability criteria failure in step 404. In step 502, the mobilewireless communication device 106 can determine if one of the cellsfound has been previously used and for which SIB values have been storedin the mobile wireless communication device 106. If one of the foundcells is the same as a previously used cell then the mobile wirelesscommunication device 106 can use stored SIB3 values to evaluate thesuitability of the cell in step 412 bypassing the MIB and SIB readingsteps 408 and 410. If the cell suitability criteria are met in step 414,then the cell selection process can continue in step 416. By identifyinga “same cell” in step 502 and bypassing the MIB/SIB steps 408/410, andwith successful suitability criteria met in step 414, the mobilewireless communication device 106 can shorten the cell selection processsignificantly by eliminating the read/evaluate cycle 418.

In order for the proposed method 500 to function properly, the wirelesscommunication network 100 can ensure that all cells found in the cellsearch of step 406 have unique primary scrambling codes (PSC) by notrepeating the use of the same PSC in a given area. This network radiofrequency planning rule can typically be employed. The mobile wirelesscommunication device 106 can determine if the primary scrambling codefound in the cell search of step 406 that matches a stored cell canactually be from the stored cell, i.e. the matching PSC does actuallyrepresent the same cell as previously used, by evaluating movements ofthe mobile communication device 106. As a representative embodiment, themobile wireless communication device 106 can store a set of locationcoordinate values (e.g. GPS values) for each cell in addition to the PSCwhen storing the SIB values internally for the cell identified by thePSC. The mobile wireless communication device 106 can compare a currentlocation coordinate value to the stored location value associated withthe matching PSC to determine if the mobile wireless communicationdevice 106 is observing the same cell. The current location value andthe stored location value need not match exactly but can be within arange of each other that represents a typical network planning distanceover which a PSC value can be considered unique. As anotherrepresentative embodiment, the mobile wireless communication device 106can estimate a distance difference between a “current” found cell fromthe cell search 406 and the “previous” cell by keeping track of theelapsed time from the cell suitability criteria failure in step 404 andusing knowledge of an average velocity of movement of the mobilewireless communication device 106.

FIG. 6 illustrates a representative method by the mobile wirelesscommunication device 106 for evaluating cell suitability and associatingwith a suitable cell in a wireless communication network 100. The mobilewireless communication device 106, in step 602, can detect a first cellfails one or more stored suitability criteria. The stored suitabilitycriteria can be stored in the mobile wireless communication device 106before detecting of the first cell failure. Cell failure can includeloss of service, loss of suitable signal strength, loss of suitablesignal quality or any other measures by which the mobile wirelesscommunication device 106 and/or the wireless communication network 100can conclude that a connection is not suitable for transmission. Inresponse to cell suitability failure, in step 604, the mobile wirelesscommunication device 106 can search for and locate a set of candidatecells with which to possibly associate in the wireless communicationnetwork 100. The set of candidate cells can include in some instancesand can not include in other instances the previously failed first cell.

In step 606, the mobile wireless communication device 106 can measure atleast one signal metric for each candidate cell in the located set ofcandidate cells. Signal metrics can include measuring a signal thatindicates a carrier frequency, a frequency channel, a frequency code, asignal code strength, a signal quality strength or any other measuresthan can identify the candidate cell and/or qualify the candidate cellas suitable to connect with by the mobile wireless communication device106. In step 608, the mobile wireless device can determine if one of thecandidate cells in the located set of candidate cells is identically thefirst cell that failed suitability in step 602. If one of the candidatecell's is identically the first cell, then the mobile wirelesscommunication device in step 610 can evaluate suitability of the firstcell using one or more of the stored suitability criteria. Evaluatingsuitability can include determining if the first cell satisfies the oneor more stored suitability criteria. The mobile wireless communicationdevice 106 can determine that the first cell is suitable in step 612 andsubsequently associated with the first cell in step 618.

If the candidate cell is not the first cell in step 608, or if the firstcell is not suitable in step 612, then the mobile wireless communicationdevice can receive suitability criteria for one or more of the candidatecells in the located set of candidate cells in step 614. The wirelesscommunication network 100 can broadcast the suitability criteria atregular intervals or according to a schedule known by or communicated tothe mobile wireless communication device 106 or by an indication on apaging channel, or by any other means by which the mobile wirelesscommunication device 106 can determine when to listen for and receivethe transmitted suitability criteria. In step 616, the mobile wirelesscommunication device 106 can evaluate each candidate cell's suitabilityusing the suitability criteria received from the wireless communicationnetwork 100. One or more of the candidate cells can satisfy thesuitability criteria. In step 618 the mobile wireless communicationdevice 106 can associate with one of the candidate cells that satisfythe suitability criteria.

FIG. 7 illustrates a representative method for testing cell suitabilityby the mobile wireless communication device 106 and associating with asuitable cell. In step 702, the mobile wireless communication device candetect a loss of connection between the mobile wireless communicationdevice 106 and a cell in the wireless communication network 100. In step704 a set of candidate cells can be located by the mobile wirelesscommunication device. Locating the candidate cells can include searchingfor cells by using information broadcast by the wireless communicationnetwork. In step 706 a subset of the set of located candidate cells canbe matched using criteria stored in the mobile wireless communicationdevice 106. In step 708, the subset of matching cells can be ranked byan estimated distance from the mobile wireless communication device'scurrent geographic position or the mobile wireless communicationdevice's past geographic position when the connection loss was detectedin step 702. Each of the matching cell's can be tested for cellsuitability in ranked order using one or more stored suitabilitycriteria in step 710. A matching cell can be found suitable in step 712,and the mobile wireless communication device 106 can select to associatewith the matching suitable cell in step 714. Checking for cellsuitability in steps 710 and 712 can proceed through all of the matchingcells in ranked order and the mobile wireless communication device 106can select to associate with a suitable cell or until all cells can befound unsuitable in step 716.

FIG. 8 illustrates processing elements of a representative mobilewireless communication device 106 including a transceiver 804 and anapplication processor 802. The mobile wireless communication device 106can transmit and receive radio frequency signals through an antenna 806connected to the transceiver. The transceiver 804 can process physicallayer radio frequency signals and link layer protocol data units. Thetransceiver 804 can transmit and receive packetized messages with theapplication processor 802, which can establish higher layer connectionsof the mobile wireless communication device 106 to endpoints through thewireless communication network 100. In some embodiments, the applicationprocessor 802 and the transceiver 804 can be included in the sameintegrated circuit device or package, while in other embodiments, theapplication processor 802 and the transceiver 804 can be separate.Detecting connection loss or cell suitability failure can occur ineither the application processor 802 or the transceiver 804 or in acombination of both as can other steps described for FIGS. 5, 6 and 7.

Various aspects of the described embodiments can be implemented bysoftware, hardware or a combination of hardware and software. Thedescribed embodiments can also be embodied as computer program code on acomputer readable medium for selecting a cell in a wireless network withwhich to associate. The computer readable medium is any data storagedevice that can store data which can thereafter be read by a computersystem. Examples of the computer readable medium include read-onlymemory, random-access memory, CD-ROMs, DVDs, magnetic tape and opticaldata storage devices. The computer readable medium can also bedistributed over network-coupled computer systems so that the computerprogram code is stored and executed in a distributed fashion.

The various aspects, embodiments, implementations or features of thedescribed embodiments can be used separately or in any combination. Theforegoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that the specificdetails are not required in order to practice the invention. Thus, theforegoing descriptions of specific embodiments of the present inventionare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed. It will be apparent to one of ordinary skill in the art thatmany modifications and variations are possible in view of the aboveteachings.

The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated.

1. A method, comprising: in a mobile wireless communication device,detecting a first wireless cell in a wireless communication networkassociated with the mobile wireless communication device that fails atleast one criterion for the first wireless cell in a set of suitabilitycriteria stored in the mobile wireless communication device, the set ofsuitability criteria including at least one of received power level andreceived signal quality parameters broadcast in one or more systeminformation blocks by the wireless communication network and stored inthe mobile wireless communication device before detecting the firstwireless cell fails the at least one criterion; searching for andlocating a set of candidate wireless cells with which to associate;measuring at least one received signal metric for each candidatewireless cell in the set of candidate wireless cells; determiningwhether a candidate wireless cell in the set of candidate wireless cellsis the first wireless cell; evaluating whether the candidate wirelesscell satisfies one or more criteria for the first wireless cell in thestored set of suitability criteria in the mobile wireless communicationdevice using the measured at least one received signal metric for thecandidate wireless cell when the candidate wireless cell is the firstwireless cell; and associating the mobile wireless communication devicewith the candidate wireless cell when the candidate wireless cell is thefirst wireless cell and satisfies one or more criteria in the stored setof suitability criteria.
 2. The method as recited in claim 1, whereinsearching for and locating the set of candidate wireless cells includesreceiving a radio frequency signal from a radio network subsystem ineach candidate wireless cell identifying the candidate wireless cell. 3.The method as recited in claim 2, wherein the received signal metricused to measure each candidate wireless cell is a measure of receivedsignal code power.
 4. The method as recited in claim 2, wherein thereceived signal metric used to measure each candidate wireless cell is achip energy.
 5. The method as recited in claim 1, wherein determiningwhether the candidate wireless cell is the first wireless cell includesestimating the candidate wireless cell's geographic location and thefirst wireless cell's geographic location.
 6. The method as recited inclaim 1, wherein determining whether the candidate wireless cell is thefirst wireless cell includes estimating changes in geographic positionof the mobile wireless communication device.
 7. The method as recited inclaim 1, further comprising: when no candidate wireless cell in the setof candidate wireless cells is the first wireless cell, receivingsuitability criteria for the set of candidate wireless cells from atleast one radio network subsystem in the wireless communication network,the suitability criteria including at least one cell selection orreselection parameter broadcast in one or more system information blocksby at least one radio network subsystem in the wireless communicationnetwork; evaluating whether a cell in the set of candidate wirelesscells satisfies one or more of the received suitability criteria; andassociating the mobile wireless communication device with the cell inthe set of candidate wireless cells, when the cell satisfies one or moreof the received suitability criteria.
 8. The method as recited in claim7, wherein the at least one radio network subsystem in the wirelesscommunication network transmits the suitability criteria using broadcastsystem information block type 3 (SIB3) or block type 11 (SIB11)messages.
 9. A mobile wireless communication device, the devicecomprising: an application processor configured to generate and receivemessages; a transceiver connected to the application processor, thetransceiver configured to transmit radio frequency signals to andreceive radio frequency signals from a wireless communication networkand configured to select a cell in the wireless communication networkwith which to connect by: detecting a loss of radio frequency connectionbetween the transceiver in the mobile wireless communication device anda first cell in the wireless communication network; locating a set ofcandidate cells in the wireless communication network with which toconnect; determining a subset of located candidate cells that match tocell suitability criteria stored in the mobile wireless communicationdevice, the cell suitability criteria including at least one of receivedpower level and received signal quality parameters broadcast in one ormore system information blocks by the wireless communication network;determining whether one of the cells in the subset of located candidatecells is the first cell to which the mobile wireless device waspreviously connected; and selecting the first cell to associate with themobile wireless communication device when the first cell satisfies oneor more of the stored cell suitability criteria, wherein the cellsuitability criteria are stored in the mobile wireless communicationdevice prior to detecting the loss of radio frequency connection. 10.The mobile wireless communication device as recited in claim 9, whereinthe transceiver is further configured to select the cell in the wirelesscommunication network with which to connect by: when none of the cellsin the subset of located candidate cells is the first cell, receivingsuitability criteria from a radio network subsystem in a locatedcandidate cell in the subset of located candidate cells; determiningwhether the located candidate cell satisfies the received suitabilitycriteria; and associating the mobile wireless communication device withthe located candidate cell when the located candidate cell satisfies thereceived suitability criteria.
 11. The mobile wireless communicationdevice as recited in claim 10, wherein locating the set of candidatecells in the wireless communication network with which to connectincludes receiving a radio frequency signal from the radio networksubsystem in each candidate wireless cell identifying the candidatewireless cell.
 12. The mobile wireless communication device as recitedin claim 10, wherein determining whether the located candidate cellsatisfies the received suitability criteria includes measuring areceived signal quality of the located candidate cell.
 13. The mobilewireless communication device as recited in claim 9, wherein theapplication processor is configured to determine whether one of thecandidate cells is the first cell to which the mobile wirelesscommunication device was previously connected by estimating the one ofthe candidate cells geographic location and the first cell's geographiclocation.
 14. The mobile wireless communication device as recited inclaim 9, wherein the application processor is further configured todetermine whether the selected cell is the first cell using a measure oftime elapsed after detecting the loss of radio frequency connectionbetween the transceiver and the first cell.
 15. The mobile wirelesscommunication device as recited in claim 9, wherein the applicationprocessor is further configured to determine whether the selected cellis the first cell using a measure of a rate of displacement of themobile wireless communication device.
 16. A non-transitory computerreadable medium for storing computer program code executable by aprocessor in a mobile wireless communication device for selecting a cellin a wireless network with which to associate comprising: in the mobilewireless communication device, computer program code for detecting afirst cell in the wireless network associated with the mobile wirelesscommunication device fails one or more suitability criteria stored inthe mobile wireless communication device, the set of suitabilitycriteria including at least one of received power level and receivedsignal quality parameters broadcast in one or more system informationblocks by the wireless communication network and stored in the mobilewireless communication device before detecting the first cell fails theone or more suitability criteria; computer program code for searchingfor and locating a set of candidate cells with which to associate themobile wireless communication device; computer program code fordetermining whether one of the candidate cells in the set of candidatecells is the first cell to which the mobile wireless communicationdevice was previously connected; computer program code for evaluatingwhether the first cell satisfies one or more stored suitability criteriafor the first wireless cell when one of the candidate cells is the firstcell; and computer program code for associating with the first cell whenone of the candidate cells in the set of candidate cells is the firstcell and the first cell satisfies one or more of the receivedsuitability criteria.
 17. The non-transitory computer readable medium asrecited in claim 16 further comprising: computer program code forreceiving suitability criteria for the set of candidate cells from thewireless network when no candidate cell is the first cell and forevaluating whether a cell in the set of candidate cells satisfies one ormore of the received suitability criteria; and computer program code forassociating with the candidate cell, when the candidate cell satisfiesone or more of the received suitability criteria.
 18. The non-transitorycomputer readable medium as recited in claim 16, wherein computerprogram code for locating the set of candidate cells includes receivinga radio frequency signal from the radio network subsystem in eachcandidate cell identifying the candidate cell.
 19. The non-transitorycomputer readable medium as recited in claim 17, wherein computerprogram code for receiving suitability criteria for the set of candidatecells from the wireless network includes receiving system informationmessages broadcast by radio network subsystems in the candidate cells.20. The non-transitory computer readable medium as recited in claim 19,wherein computer program code for determining whether one of thecandidate cells in the set of candidate cells is the first cell includesreceiving master information messages broadcast by radio networksubsystems in the candidate cells.
 21. The non-transitory computerreadable medium as recited in claim 16, wherein computer program codefor determining whether the candidate wireless cell is the firstwireless cell includes estimating changes in geographic position of themobile wireless communication device.
 22. The non-transitory computerreadable medium as recited in claim 16, wherein computer program codefor determining whether the candidate wireless cell is the firstwireless cell includes measuring time elapsed after detecting the firstcell fails one or more stored suitability criteria.
 23. Thenon-transitory computer readable medium as recited in claim 17, whereincomputer program code for determining whether the candidate wirelesscell is the first wireless cell includes estimating the candidatewireless cell's geographic location and the first wireless cell'sgeographic location.